A TimThumb error has occured

The following error(s) occured:

The remote file is not a valid image. Mimetype = 'text/html' File = /var/www/html/timthumb/cache/timthumbp5uLLb

Query String : h=480&zc=1&a=c&src=http://www.campingmarinadiroma.it/gestione/uploads/photo/12031__GPP9954_(Large).jpg
TimThumb version : 2.8.13